Tseng turned pro with the China Times Eagles in 1993. He hit .337/.379/.477 and led the CPBL in hits (109) and average. He was named the CPBL Rookie of the Year and made the Best Ten as one of the loop's top three outfielders. He batted .340/.418/.442 in 1994 and led the league in OBP but was .020 behind average leader Angel Gonzalez. He tied George Hinshaw for 5th in the league in average.

In '95, the Kaohsiung native fell to .306/.367/.424 with a league-best 70 runs, his worst year as a pro. He was still 8th in the CPBL in average, 5th among native-born players. He hit .345/.398/.481 with 17 steals in 23 tries, 78 runs in 99 games and a CPBL-record 143 hits in 1996. It would be 11 years before Kuo-Ching Kao broke the hit mark, though Tseng had only led the loop by two over Hector Roa. He finished 6th in the circuit in average He won a Gold Glove for his outfield defense and made his second Best Ten, joining Chuan-Chia Wang and Sil Campusano in the outfield.

Tseng began 1997 even better, hitting .368/.427/.561 in 43 games before being banned for life from the CPBL for his involvement in one of the game-fixing scandals to plague Taiwan. He had a career line of .335/.394/.466.